A level shifter is commonly used in an integrated circuit. For example, in some applications, the level shifter is arranged between an input/output (I/O) circuit and a core circuit of an electronic device (e.g., memory device). With the development of the process technology, the operating voltage of the core circuit becomes lower, and the operating voltage of the core circuit is thus lower than the operating voltage of the I/O circuit. Accordingly, before a signal is transmitted from the core circuit to the I/O circuit, a voltage level of the signal is able to be increased by the level shifter. Alternatively, before a signal is transmitted from the I/O circuit to the core circuit, a voltage level of the signal is able to be decreased by the level shifter.